U.S. patent application number 13/787915 was filed with the patent office on 2014-09-11 for manufacturing method of cathode catalyst and ozone-generating device.
This patent application is currently assigned to CASHIDO CORPORATION. The applicant listed for this patent is CASHIDO CORPORATION. Invention is credited to SHIH-CHANG CHEN, SYUAN-HONG CHEN, LIANG-CHIEN CHENG, CHUN-LUNG CHIU, I-CHIAO LIN, RU-SHI LIU, LING-HUI LU, CHIEN-MIN SUNG, HSIU-LI WEN.
Application Number | 20140251795 13/787915 |
Document ID | / |
Family ID | 51486485 |
Filed Date | 2014-09-11 |
United States Patent
Application |
20140251795 |
Kind Code |
A1 |
CHEN; SHIH-CHANG ; et
al. |
September 11, 2014 |
MANUFACTURING METHOD OF CATHODE CATALYST AND OZONE-GENERATING
DEVICE
Abstract
The instant disclosure relates to a manufacturing method of
cathode catalyst, comprising the following steps. Initially, mix an
organic medium with an iron-based starting material and a
nitrogen-based starting material to form a mixture. Followed by
adding a carbon material to the mixture and subsequently executing
a heating process to form a solid-state precursor. Then mill the
solid-state precursor to form a precursory powder. Successively,
calcinate the precursory powder in the presence of NH.sub.3 to form
a cathode catalyst. The cathode catalyst can reduce the activation
energy of hydrogen ion reacting with oxygen to make water. The
instant disclosure further provides an ozone-generating device.
Inventors: |
CHEN; SHIH-CHANG; (HSINCHU
COUNTY, TW) ; CHEN; SYUAN-HONG; (MIAOLI COUNTY,
TW) ; CHENG; LIANG-CHIEN; (KAOHSIUNG CITY, TW)
; LIU; RU-SHI; (NEW TAIPEI CITY, TW) ; LIN;
I-CHIAO; (TAIPEI CITY, TW) ; CHIU; CHUN-LUNG;
(HSINCHU COUNTY, TW) ; LU; LING-HUI; (MIAOLI
COUNTY, TW) ; WEN; HSIU-LI; (MIAOLI COUNTY, TW)
; SUNG; CHIEN-MIN; (NEW TAIPEI CITY, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CASHIDO CORPORATION |
Miaoli County |
|
TW |
|
|
Assignee: |
CASHIDO CORPORATION
MIAOLI COUNTY
TW
|
Family ID: |
51486485 |
Appl. No.: |
13/787915 |
Filed: |
March 7, 2013 |
Current U.S.
Class: |
204/252 ;
502/180 |
Current CPC
Class: |
B01J 27/24 20130101;
C25B 9/08 20130101; C25B 11/0442 20130101; C25B 11/0489 20130101;
C25B 1/13 20130101; C25B 9/10 20130101 |
Class at
Publication: |
204/252 ;
502/180 |
International
Class: |
B01J 27/24 20060101
B01J027/24; C25B 1/13 20060101 C25B001/13; C25B 11/04 20060101
C25B011/04; C25B 9/10 20060101 C25B009/10 |
Claims
1. A method for manufacturing a cathode catalyst, comprising steps
of: mixing a starting material having at least iron and another
starting material having at least nitrogen into an organic medium
to form a mixture; adding a carbon material into the mixture and
heat-treating the mixture to form a solid precursor; milling the
solid precursor to form a powder precursor; and calcining the
powder precursor in the presence of ammonia to form the cathode
catalyst.
2. The method as recited in claim 1, wherein the starting material
having at least iron is selected from the group consisting of
ferrous acetate, ferrous sulfate, and ferrous oxalate and the
starting material having at least nitrogen is phosphorus
phenanthroline.
3. The method as recited in claim 1, wherein the organic medium is
selected from the group consisting of methanol, ethanol, butanol,
isopropanol, and propanol.
4. The method as recited in claim 1, wherein the starting material
having at least iron and the starting material having at least
nitrogen have a respective molarity ratio of about 1.5 to 2.8: 11.1
and are mixed into the organic medium.
5. The method as recited in claim 1, wherein the carbon material is
selected from the group consisting of carbon black, graphite
whiskers, amorphous carbon, activated carbon, mesoporous carbon,
porous carbon fiber, carbon nanofiber, carbon nanotubes and carbon
fibers, and heat-treated via an oven at a temperature between
60.degree. C. to 80.degree. C. for about 8 to 16 hours.
6. The method as recited in claim 1, wherein in the milling step,
the solid precursor is milled by zirconium ball in a milling tank
for about 2 to 4 hours to form the powder precursor.
7. The method as recited in claim 1, wherein in the calcining step,
the powder precursor is heated in a high temperature furnace at a
temperature between 500.degree. C. to 1000.degree. C. for about 1
to 3 hours in the presence of ammonia gas to form the cathode
catalyst.
8. An ozone generating device, comprising: a cation exchange
membrane; an anode reservoir having an anode formed on a face of
the cation exchange membrane and arranged proximate to a side of
the cation exchange membrane, the anode including an anode
substrate and an anode catalyst layer coating on the anode
substrate; and a cathode reservoir having a cathode formed on the
other face of the cation exchange membrane and arranged proximate
to the other side of the cation exchange membrane, and the cathode
including a cathode substrate having the cathode catalyst made by
the method of claim 1 and a cathode catalyst layer coating on the
cathode substrate;
9. The device as recited in claim 8, wherein the anode substrate is
selected from the group consisting of carbon paper and carbon
fabric, and the cathode substrate is selected from the group
consisting of platinum, copper, silicon dioxide, lead dioxide,
carbon fabric, carbon paper, and a combination thereof.
10. The device as recited in claim 8, wherein the cathode catalyst
layer is formed by mixing the cathode catalyst and a resin into a
paste like mixture, subsequently coating the paste like mixture on
a surface of the cathode substrate, and successively drying the
past like mixture.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The instant disclosure relates to a cathode catalyst; in
particular, to a cathode catalyst which is applied with an ozone
generating device for catalyzing hydrogen ions generated from an
anode to react and generate water and preventing production of
hydrogen gas.
[0003] 2. Description of Related Art
[0004] Ozone is known as a fairly powerful natural oxidizing agent,
whose oxidizing power is 3000 times stronger than chloride, and
unlike chloride which will remains in the environment for a long
period of time, resulting in the rapid and extended use of ozone in
various industries.
[0005] Presently, common ozone manufacturing methods include
ultraviolet light, Corona discharge method and electrolytic ozone
generation, etc. Of the three methods, ultraviolent light and
Corona discharge method are commonly applied in the industry and
household sector with deficiencies such as relatively high energy
consumption, complex system composition, high production cost, and
requiring ozone gas to dissolve in liquid water, therefore, the
rise of water electrolytic ozone generating technology.
[0006] In general, water electrolysis ozone generating devices
includes a solid polymer electrolyte membrane (cation exchange
membrane) and the sealed anode and cathode arranged on two sides
thereof. Successively, water electrolysis reactions take place
between the three phases (three phase interface), the cation
exchange membrane, the electrode catalyst (such as the anode
electrode catalyst of iridium, a cathode electrode catalyst using
platinum-carbon catalyst), and liquid phase for generating ozone
from the anode and hydrogen gas from the cathode.
[0007] However, during electrolysis, the hydrogen gas generated
from the three phase interface among cathode catalyst, cation
exchange membrane and water will permeate through the cation
exchange membrane, reach the cathode, mix with oxygen, and
outwardly discharge via the pressure inside bubbles as a driving
force.
[0008] According to the Young-Laplace equation
(P.sub.g-P.sub.L=2.gamma./r, where P.sub.g: bubble internal
pressure; P.sub.L: liquid pressure; y: the surface tension of the
liquid; r: radius of the bubble), when liquid pressure is fixed,
the smaller the radius of the bubble, the larger the internal
pressure therein, which correspondingly leads to a decline in the
ozone purity or the current efficiency of the gas generated (i.e.
degradation in the performance of a water ozone generating
device).
[0009] Moreover, during the generation of ozone, oxygen, and
hydrogen in the ozone generating device, since hydrogen gas move
towards the cathode (4.65% volume of an ozone, oxygen, and hydrogen
gas mixture is hydrogen gas), the lower explosion limit of hydrogen
might be exceeded. Particularly, when electrodes produce high
concentration of gas at a relatively high current density, device
safety is likely to become a concern. Moreover, the resulting
hydrogen ion generated can easily lead to electrode corrosion which
reduces the usable life of the electrodes.
[0010] To address the above issues, the inventor strives via
associated experience and research to present the instant
disclosure, which can effectively improve the limitation described
above.
SUMMARY OF THE INVENTION
[0011] The object of the instant disclosure is to provide a
manufacturing method for a cathode catalyst suitable for an ozone
generating device which can generate ozone for an extended period.
The cathode catalyst can prevent the generation of hydrogen gas
which is a safety concern, thus, increase the stability of the
ozone generating device.
[0012] According to a first embodiment of the instant disclosure,
the manufacturing method of the cathode catalyst comprises an
iron-based starting material and a nitrogen-based starting material
mixed into an organic medium, thus, forming a mixture. Then, a
carbon material is added into the mixture and heat-treated to form
a solid precursor. Thereafter, the solid precursor undergoes
milling to form a precursor powder, and successively, the precursor
powder is calcinated in the presence of ammonia to form the cathode
catalyst.
[0013] According to the aforementioned cathode catalyst, the
instant disclosure further provides an ozone generating device
comprises a cation exchange membrane, an anode reservoir, and a
cathode reservoir. The anode reservoir is arranged on a side of the
cation exchange membrane and has an anode in contact with a face of
the cation exchange membrane, in which the anode comprises an anode
substrate and an anode catalyst layer formed on the anode
substrate. The cathode reservoir is arranged on the other side of
the cation exchange membrane, in which the cathode comprises a
cathode substrate and a cathode catalyst layer formed on the
cathode substrate. The cathode catalyst layer comprises the cathode
catalyst made from the aforementioned manufacturing method.
[0014] In summary, the cathode catalyst in accordance with the
embodiments of the instant disclosure comprises at least three
elements: iron, nitrogen, and carbon. When the anode of the ozone
generating device transforms water into ozone, the by-products,
hydrogen ions, will permeate through the cation exchange membrane
to the cathode. The hydrogen ions react with the cathode catalyst
of the instant disclosure via an oxidation reaction to produce
water, which can effectively prevent hydrogen gas generation, a
safety concern, lower the possibility of hydrogen ion corrosion to
electrodes, and increase safety and stability of the ozone
generating device.
[0015] In order to further understand the instant disclosure, the
following embodiments and illustrations are provided. However, the
detailed description and drawings are merely illustrative of the
disclosure, rather than limiting the scope being defined by the
appended claims and equivalents thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a cross-sectional view illustrating the ozone
generating device of the instant disclosure;
[0017] FIG. 2 is a flow diagram illustrating the cathode catalyst
manufacturing method of the instant disclosure;
[0018] FIG. 3 is an X-ray diffraction pattern graph of cathode
catalysts made at different calcination temperature of the instant
disclosure;
[0019] FIG. 4 is a graph of the instant disclosure illustrating the
oxygen reduction reactivity with respect to cathode catalysts made
at different calcination temperature;
[0020] FIG. 5 is a graph of the instant disclosure illustrating the
relationships of the hydrogen peroxide generation rate and the
number of electrons transferred with respect to the electric
potential of cathode catalysts made at different calcination
temperature; and
[0021] FIG. 6 is a graph of the instant disclosure illustrating the
electric potential of three different iron-based starting
materials.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] The aforementioned illustrations and detailed descriptions
are exemplarities for the purpose of further explaining the scope
of the instant disclosure. Other objectives and advantages related
to the instant disclosure will be illustrated in the subsequent
descriptions and appended drawings.
[0023] The following is a more detailed description of the
manufacturing method of an ozone generating device and a cathode
catalyst according to the instant disclosure, in which the ozone
generating device can consistently generate ozone for an extensive
amount of time.
[0024] Please refer to FIG. 1 as a top view of the instant
disclosure. An ozone generating device 100 comprises a cation
exchange membrane 1, an anode reservoir 2, and a cathode reservoir
3. The anode reservoir 2 is arranged proximate to a side of the
cation exchange membrane 1 and have an anode 21 formed on a face of
the cation exchange membrane 1. Furthermore, an anode chamber 22 is
defined between the anode 21 and the anode reservoir 2. The anode
21 includes an anode substrate 211 upon which an anode catalyst
layer 212 is supported. The anode substrate is a conductive porous
structure. Specifically, the anode catalyst layer 212 is applied on
a face of the anode substrate 211 while the other face contacts the
cation exchange membrane 1 for generating ozone.
[0025] The cathode reservoir 3 is arranged proximate to another
side of the cation exchange membrane 1 and has a cathode 31 formed
on the other face of the cation exchange membrane 1. Furthermore, a
cathode chamber 32 is defined between the cathode 31 and the
cathode reservoir 3. The cathode 31 includes a cathode substrate
311 upon which a cathode catalyst layer 312 is supported.
Specifically, the cathode catalyst layer 312 is applied on a face
of the cathode substrate 311 while the other face contacts the
cation exchange membrane 1 for generating hydroxide.
[0026] In the instant embodiment, the membrane 1 is preferably a
perfluorosulfonic acid cation exchange membrane which has high
cation selective permeability, high chemical and thermal stability,
high mechanical strength, low-electrolyte diffusion rate, and a low
resistance, etc.
[0027] Proximate to an anodic portion of the cation exchange
membrane 1, the anode substrate 211 is generally a structure having
conductivity and corrosion resistance to antioxidants such that the
gas produced can be fully released and the electrolyte can
circulate adequately. For example, sheet or rolled form of carbon
fiber body (carbon paper or carbon cloth) or metals such as
titanium, tantalum, niobium, and zirconium as the substrate
material having the form of a porous body, mesh body, fibrous body,
foamed body, but not limited thereto. Furthermore, the porous body
can be formed by mixing fluororesin with metal particles, in which
the fluororesin is preferably polytetrafluoroethylene (PTFE).
Alternatively, the porous body can be porous metal plate or a metal
fiber sintered body.
[0028] The anode catalyst layer 212 may be formed on the surface of
the anode substrate 211 with materials having relatively high
oxygen overvoltage through a process such as electroplating,
thermal decomposition, coating, hot pressing, etc. The anode
catalyst layer 212 may be lead dioxide or conductive diamond.
[0029] Proximate to a cathodic portion of the cation exchange
membrane 1, the cathode substrate 311 can be sheet or rolled form
of carbon fiber body (carbon paper or carbon cloth) or metals such
as nickel, stainless steel, and zirconium as the substrate material
having the form of a porous body, mesh body, fibrous body, foamed
body, but not limited thereto. More importantly, the cathode
catalyst layer 312 of the instant disclosure comprises a cathode
catalyst made from the following manufacturing method.
[0030] Please refer to FIG. 2 as the process flow diagram of the
manufacturing method for a first embodiment of the instant
disclosure. Initially, an iron-based starting material and a
nitrogen-based starting material are mixed into an organic medium
to form a mixture. In the instant embodiment, the iron-based
starting material is ferrous acetate (Fe
(C.sub.2H.sub.3O.sub.2).sub.2) while the nitrogen-based starting
material is phosphorus phenanthroline and the organic medium is
ethanol. Then, ferrous acetate and phosphorus phenanthroline are
mixed into ethanol at a molarity ratio of 1.7:11.1 and further
homogeneously mixed for about 12 hours to form the mixture. During
the mixing process, a chelate is formed by iron ions of the ferrous
acetate and phosphorus phenanthroline and the mixture is then
dissolved in ethanol.
[0031] Thereafter, a carbon material is added into the mixture and
undergoes a heat-treating process to form a solid precursor.
Specifically, the carbon material can be carbon black, graphite
whiskers, amorphous carbon, activated carbon, mesoporous carbon,
porous carbon fiber, carbon nanofiber, carbon nanotubes or carbon
fibers. Particle size of the carbon material is less than 10
microns. Subsequently, the mixture having the carbon material is
placed into an oven for the heat-treating process at a temperature
between 60.degree. C. to 80.degree. C., and then maintained
temperature for about 8 to 16 hours for removing the solvent to
form the solid precursor.
[0032] Next, the solid precursor is milled into a powder precursor.
During milling, the solid precursor is placed in a milling tank and
undergoes milling via zirconium ball for about 2 to 4 hours to form
the powder precursor.
[0033] Successively, the powder precursor is calcined in the
presence of ammonia to form the cathode catalyst. During
calcination, the power precursor is placed in a high-temperature
furnace in the presence of ammonia, and calcining at a temperature
between 500.degree. C. to 1000.degree. C. for about 1 to 3 hours to
form the powder form of cathode catalyst which includes at least
three elements: iron, nitrogen, and carbon. Furthermore, the powder
form cathode catalyst is first mixed with a resin to form a paste
like mixture, then coated on a surface of the cathode substrate
311, and thereafter dried to form the cathode catalyst layer
312.
[0034] As shown in FIG. 3 is an X-ray diffraction pattern graph of
cathode catalysts made at different calcination temperature
specifically illustrating the crystalline phase during each process
from mixing the material to milling the solid precursor into the
powder precursor. As illustrated, between 500.degree. C. to
600.degree. C., calcinated catalysts shows no significance of
Fe.sub.2N phase growth whereas between 700.degree. C. to
900.degree. C., calcinated catalysts shows relatively higher
significance of Fe.sub.2N phase growth, and at around 1000.degree.
C., Fe.sub.2N in calcinated catalysts completely transformed into
FeN.sub.0.056.
[0035] As shown in FIG. 4 is a graph of the oxygen reduction
reactivity with respect to cathode catalysts made at different
calcination temperature, in which the Y axis respectively shows
from top to bottom the density of the ring current and the disc
current. Specifically, catalysts made at different calcination
temperature are formed on the disc electrode of the rotating
ring-disc electrode (RRDE), and using linear voltammetry to measure
the redox reaction (oxygen reduction reaction, ORP) activity in an
0.5M aqueous solution of oxygen-rich sulfuric acid.
[0036] As illustrated in figures, the half-wave potential of the
cathode catalyst in the instant disclosure shifts towards the high
potential as the calcination temperature rises which means that the
redox reaction activity increases as the calcination temperature
rises. However, when the calcination temperature exceeds
800.degree. C., the half-wave potential will shifts towards the low
potential as the calcination temperature continues to rise. In
addition, catalytic activity results derived from theoretical
calculations in literatures point out that the onset potential of
the catalyst will determine the adsorption energy of the oxygen
adsorbed on the surface of the catalyst. In other words, the lower
the onset potential the higher the starting potential.
[0037] Therefore, cathode catalysts calcined at a calcination
temperature between 700.degree. C. to 800.degree. C. not only has
the highest half-wave potential, but can also effectively reduce
the adsorption energy of oxygen. As a result, a temperature between
700.degree. C. to 800.degree. C. is the most preferably calcining
temperature.
[0038] As illustrated in FIG. 5 is the graph illustrating the
relationships of the hydrogen peroxide generation rate and the
number of electrons transferred with respect to the electric
potential of cathode catalysts made at different calcination
temperature. As shown, cathode catalysts at a calcination
temperature between 500.degree. C. to 800.degree. C. will catalyze
a redox reaction path involving four electrons (as shown in
chemical reaction 1 below) while the calcinated catalysts at a
calcination temperature between 900.degree. C. to 1000.degree. C.
will catalyze a redox reaction involving two electrons (as shown in
chemical reaction 2 below) and resulting in higher concentrations
of hydrogen peroxide.
O2+4H++4e-.fwdarw.2H2O (Reaction 1)
O2+2H++2e-.fwdarw.H2O2 (Reaction 2)
[0039] As mentioned above, the cathode catalysts of the instant
disclosure includes Fe.sub.2N, and the Fe.sub.2N is formed on the
carbon carriers which can catalyze hydrogen and oxygen ions to form
water through a four-electron transfer reaction. In other words, by
applying the ozone generating device 100 with the aforementioned
cathode catalysts, hydrogen ions generated from the anode 21 can
transform into water to prevent hydrogen gas from generating, as a
result increasing the safety and stability of the ozone generating
device 100. Moreover, the ozone generating device 100 may also
prevent electrodes from corrosion subjected to hydrogen ions,
thereby extending the usable life of electrodes.
Second Embodiment
[0040] Please refer to FIG. 6 as the graph illustrating electric
potentials of the three different iron-based starting materials.
The iron ion activity of ferrous acetate (Fe
(C.sub.2H.sub.3O.sub.2).sub.2), ferrous sulfate (FeSO.sub.4), and
ferrous oxalate (FeC.sub.2O.sub.4) can be derived from the
respective slope of the current density, in which the greater the
slope is more preferable.
[0041] As illustrated, the three starting materials show no
significant difference therebetween, therefore, the iron-based
starting material can be ferrous sulfate or ferrous oxalate.
Furthermore, ferrous sulfate and phosphorus phenanthroline are
mixed into ethanol at a molarity ratio of 2.8: 11.1,
respectively.
[0042] Moreover, ferrous oxalate and phosphorus phenanthroline are
mixed into ethanol at a molarity ratio of 1.5: 11.1, respectively,
to form a mixture. In addition, the organic medium can be one
selected from methanol, ethanol, butanol, isopropanol, and
propanol. Thereafter, continue with the remaining steps to make the
cathode catalyst of the instant disclosure.
[0043] In summary, the instant embodiments of the cathode catalyst
and ozone generating device have the following objectives. The
aforementioned manufacturing method is simple, rapid, and lower
cost than platinum and other catalysts of precious metals,
therefore, of great value. Furthermore, cathode catalyst made by
the aforementioned manufacturing method has 4-electron transport
efficiency which can catalyze hydrogen and oxygen ions via a
4-electron transport reaction to produce water, prevent hydrogen
from corroding the electrodes, and reduce the probability of the
secondary reaction of a 2-electron transport to produce hydrogen
peroxide. In addition, when the anode of the ozone generating
device 100 transforms water into ozone gas, the by-products,
hydrogen ions, will permeate through the cation exchange membrane 1
to the cathode 31 and react with the aforementioned cathode
catalyst via an oxygen reaction to produce water which effectively
prevent the safety concern of hydrogen gas generation, lower the
possibility of hydrogen corrosion on electrodes, and increase
safety and stability of the ozone generating device 100.
[0044] The figures and descriptions supra set forth illustrated the
preferred embodiments of the instant disclosure; however, the
characteristics of the instant disclosure are by no means
restricted thereto. All changes, alternations, combinations or
modifications conveniently considered by those skilled in the art
are deemed to be encompassed within the scope of the instant
disclosure delineated by the following claims.
* * * * *